In polyurethane foam manufacturing, surfactants are needed to stabilize the foam until the product-forming chemical reaction is sufficiently complete so that the foam supports itself and does not suffer objectionable collapse.
High potency surfactants, generally understood to be those which give a high height of rise and little top collapse, are desirable, because foams which collapse to a substantial degree before setting have high densities and objectionable density gradients.
Surfactants are relatively expensive. Accordingly, processors prefer to use as little as possible, employing only as much as required for desired performance. Processors also desire that the properties of the final product be relatively constant as a function of the amount of surfactant used, so that surfactant levels can be varied in the manufacturing process to give good processing, without greatly affecting the properties of the product.
Silicone surfactants for polyurethane foam manufacture typically are materials having siloxane backbones and polyether pendant groups. They are of two types, nonhydrolyzable and hydrolyzable. The nonhydrolyzable surfactants, in which the polyether pendant groups are attached to the siloxane backbone by Si--C bonds, are generally believed to have high potency but to produce "tight" foams with poor breathability. Hydrolyzable surfactants, in which the polyether pendant groups are attached to the siloxane backbone by Si--bonds, are generally believed to have poor potency but to offer good processing characteristics, and to produce foams with good breathability.
Some investigators are now questioning such generalizations and are attempting to discover silicone surfactants which have high potency, provide good processing characteristics, and produce foams having good breathability, by varying the structure of the surfactant appropriately.
Examples of such materials are described in U.S. Pat. No. 4,147,847. This patent describes certain siloxane-oxyalkylene copolymer silicone surfactants having ratios of (CH.sub.3)2SiO.sub.2/2 units to (CH.sub.3)(R)SiO.sub.2/2 units in the range of 3.5:1 to 15:1, for use in flame retardant polyurethane compositions. Other examples are surfactants having cyclic siloxane pendant groups as well as polyether pendants, described in U.S. Pat. No. 4,855,379.
It would be desirable to have nonhydrolyzable silicone surfactants which have high potency, offer good processing characteristics, produce foams having good breathability, and which function well in flame retardant formulations. Such surfactants are the subject of the present application.